DC-DC converters, as an example of power converters, are often used in electronic devices, electronic systems, and the like. DC-DC converters normally use a switch circuit comprised of switching elements and an inductor, and perform on-off control of the switching elements to convert, via the switching elements and inductor, an input DC voltage into an output DC voltage different from the input DC voltage.
These DC-DC converters are classified broadly into voltage-mode control DC-DC converters and current-mode control DC-DC converters. A voltage-mode control DC-DC converter is designed to perform on-off control of each of the switching elements using a voltage feedback loop of its output voltage. In contrast, a current-mode DC-DC converter is designed to perform on-off control of each of the switching elements using the combination of the voltage feedback loop and a current feedback loop of a current flowing through the inductor as an inductor current.
A current-mode DC-DC converter performs feedback control that:
measures the difference of a measured output voltage and a target voltage;
performs a PI algorithm based on a proportional gain term and an integral gain term using the difference as an input of the PI algorithm to thereby determine a target value of an input current, which is an example of an input electrical parameter supplied to the switch circuit, which reduces the difference;
compares a measured value of the input current to the DC-DC converter with the target value of the input current to obtain the difference between the measured value and the target value of the input current; and
determines a manipulated variable for each of the switching elements, thus reducing the difference between the measured value and the target value of the input current.
In such a current-mode DC-DC converter, there have been disclosed some technologies for reducing an overshoot of an output voltage occurring when the DC-DC converter is activated; one example of these technologies is disclosed in Japanese Patent Application Publication No. 2009-118571.
The technology applied in a DC-DC converter disclosed in the Patent Publication reduces a value of the integral gain term when the DC-DC converter is activated in comparison to a normal value of the integral gain term used when the DC-DC converter is operating normally. This reduces the increase of the output voltage based on the proportional gain term, thus preventing the occurrence of an overshoot of the output voltage.